Big renin is a larger (molecular weight 60,000 vs. 40,000 for normal renin), relatively inactve renin which is present in large amounts in plasma of patients with Wilms' tumor and other kidney tumors which cause hyperreninism, with hypertension and hyperaldosteronism. Big renin may replace normal renin in plasma of patients with diabetic nephropathy, resulting in hyporeninism, hypoaldosteronism, and hyperkalemia. The proposed research involves further study of the origin, nature, and occurrence of big renin, including the significance of activation by acid, proteases, or cold storage. Study will determine whether big renin is a prorenin (precursor of normal renin) or if it represents a reversible combination of renin with an inhibitor. The source and significance of big renin in plasma during normal pregnancy will be investigated.